The invention relates to a divided flywheel consisting of a primary flywheel mass connected secured against rotation with the drive shaft of an internal combustion engine, and a secondary flywheel mass wherein the two flywheel masses are mounted one on the other and able to rotate opposite one another relatively against the action of a damping device and the primary flywheel mass supports on its radially outer circumference a rotor of an electric machine.
A damping device with an integrated electric machine whose rotor is attached to the external circumference of the flywheel is known from DE OS 30 13 424. Devices of this kind are mainly used for starting up the internal combustion engine and for producing power in an electric machine as well as hybrid drives.
With one design mentioned at the beginning a torsional vibration damper is provided between the flywheel and gear input shaft and only dampens torsional vibrations coming from the internal combustion engine when the clutch is engaged.
Furthermore these devices have their own torsional vibration forms which lie in the region of the used speed band of the internal combustion engines and thus create loss of comfort in the drive train.
Divided flywheels which do not have these faults are adequately knownxe2x80x94such as for example from DE 36 10 127 C2xe2x80x94without a rotor.
Divided flywheels of this kind are mainly filled with grease or oil and have the drawback that increased amounts of heat supplied through blind performances of the electric machine through the rotor, and thus raised operating temperatures, cause a severely fluctuating damping behaviour and/or dilution or liquefying of the oil or grease.
The object of the present invention is therefore to provide a damping device for a device having an electric machine rotating coaxially about the axis of rotation of the internal combustion engine, which has a high damping comfort over the entire speed range with simultaneous stability in respect of the temperature fluctuations which are introduced through the electric machine, and which can be housed in an installation space provided axially and radially by the electric machine. Furthermore this device is to be produced cost-effectively by using easily manufactured individual parts and is to be simple to assemble.
The flywheel according to the invention having the rotor attached to the primary flywheel disc is in active electric connection by its rotor with the stator of the electric machine which is connected directly or indirectly to the motor housing and/or to the gearbox housing.
The flywheel according to the invention having a rotor attached to the primary flywheel disc is in electric connection by its rotor with the stator of the electric machine which is connected directly or indirectly to the motor housing and/or to the gearbox housing.
According to the present invention this is achieved in that a divided flywheel is proposed consisting of a primary flywheel mass connected secured against rotation to the drive shaft of an internal combustion engine and of a secondary flywheel mass, wherein the flywheel masses are mounted one on the other and able to rotate relative to each other against the action of a damping device, and that the primary flywheel mass consists at least of a flywheel disc connected to the drive shaft and having on its outer circumference an axially aligned ring-shaped platform on which the rotor of an electric machine is fixed, with the secondary flywheel mass having a flywheel disc which supports a clutch for coupling and uncoupling a following unit in the force flow.
Through this bell-shaped impression of the primary flywheel disc which can be produced by cold reshaping technology an assembly is formed which supports the rotor substantially freely by holding the rotor on its axially extending external circumference without forming thermal bridges for a heat flow from the rotor to the damping device. The result of this is that the divided flywheel has a thermal barrier between the rotor and damping device, i.e. the damping device is thermally uncoupled from the rotor.
It is thereby expedient if the thermal uncoupling takes place through an air gap formed between the radially outer circumference of the damping device and the axially extending platform holding the rotor on the outer circumference of the primary flywheel disc. Also the system of air gaps between the primary and/or secondary flywheel disc on one side and the damping device on the other can produce a cooling action, particularly when the air gaps are automatically ventilated through the rotation of the flywheel during operation.
For this purpose in order to ventilate these air gaps and thus the damping device a sufficient number of air slits can be provided in one or both flywheel discs where they are spread out round a circumference whose diameter is preferably the diameter of the circumference of the chamber formed by the side parts of a flywheel disc and holding the energy accumulator of the damping device, and thus the grease or oil introduced for lubrication and when using hydraulic systemsxe2x80x94for example according to DE 36 10 127 C2xe2x80x94for damping is cooled and thus produces ideal constant damping conditions.
In further embodiments insulating materials of any kind, such as for example ceramic and/or plastics can be provided between the rotor and damping device to produce a thermal insulation between the damping device and rotor.
Likewise the fastening device for the rotor on the secondary flywheel disc and/or the rotor can have on the circumferential side a groove-shaped profile, for example axially running grooves which reduces the effective bearing surface of the rotor and thus creates a thermal insulating effect.
This profile can be imprinted so that the rotation of the flywheel produces an automatic ventilation for example through air guide plates or through a suitably shaped fastening device.
According to the invention the rotor or a device enclosing same for fixing purposes can be connected with keyed engagement by an internal profiled section to the ring surface having an external profiled section wherein the internal profile has internal gearing with at least one tooth and the external profile has external gearing with at least one tooth gap, more advantageously however gearing with evenly spaced teeth and tooth gaps is. the preferred means.
A further variation is the use of at least one groove and one spring complementary therewith as the external and internal profile producing the positive locking engagement.
In order to secure the axial strength in addition axial welding is provided between the ring face and rotor which in a corresponding design can also alone form the connection.
To this end a flat surface welding is carried out radially on the external and internal circumferences of the ring face and rotor, for example by means of the impulse welding process. Furthermore the rotor can be pressed and/or staked onto the ring face. Riveting is likewise recommended, for example between a further flange-like radially outwardly extending shaped area which adjoins the axial path of the platform and can serve at the same time as an axial stop for the rotor whereby rivets in the axial direction over a preset circumference can produce the connection with the rotor.
A further inventive idea proposes dividing the primary flywheel disc into two parts, namely into a radially outer support part relative to the circle of holes for fixing the flywheel on the drive shaft, and which holds the rotor, and into a radially inner bearing pin forming the bearing for the secondary flywheel disc.
The advantage here is the easier production of two less complex disc parts Both parts are housed and centred on centring noses which can be attached to the drive shaft or a component part connected therewith wherein a sequential build-up of several discs can be formed in the axial direction in addition a disc can be added forming the input part of the damping device and which can likewise be attached on the drive shaft with the same fastening meansxe2x80x94wherein each disc is centred on the disc below.
The mutual bearing of the two flywheel disc parts on each other is undertaken by means of sliding or rolling bearings wherein the primary flywheel disc can be mounted on the secondary flywheel disc and the secondary flywheel disc can be mounted on the primary flywheel disc.
Likewise the bearing can be provided radially outside and radially inside the fastening device on the drive shaft wherein for reasons of costs the radially inner attachment is preferred and for reasons of stability the radially outer bearing can be preferred. When using a sliding bearing the use of an axial stop is advisable. According to the invention a ring-shaped stop with a rectangular profile is used.
In order to stabilise the shafts of the gearbox and internal combustion engine which are ideally aligned with no stagger relative to each other a pilot bearing can be provided which is fitted into a centring bore of a flywheel disc preferably in the primary disc or correspondingly in its bearing pin and holds the gearbox shaft. In order to rule out excess wear and avoid a hardening process for the flywheel disc or bearing pin it is possible to provide a bearing bush between the flywheel disc (bearing pin) and the pilot bearing.
In accordance with the invention the two flywheel discs are rotatable relative to each other wherein they can be turned against the action of the damping device. For this each flywheel disc has at least one biasing device for the energy accumulators, at least two coil compression springs which are spread out round a preset circumference and which are boxed in each other and pre-curved approximately to their insert diameter and/or can be short relative to the insert circumference and are provided in a suitable number.
The chamber containing the energy accumulator is formed by one of the two flywheel discs wherein axial indentations define the coil compression springs in their extension on the circumferential side and thus form the biasing device of the corresponding flywheel disc.
On its outer circumference anti-wear shells can be attached in the chamber between the inside wall of the chamber and the coil compression springs to minimize the friction of the springs and the inside wall of the chamber by adapting to the hardness of the contact faces. The use of grease as a lubricant is possible as an alternative or in addition.
The chamber can be formed in one piece out from the flywheel disc or from two connected parts of the flywheel disc. In order to optimise the thermal uncoupling it is also possible to shape a side part which is connected only to the fastening devices on the drive shaft with the primary flywheel disc in order to form the chamber so that this forms the input part of the damping device. The output part is in this case formed as a flange connected radially inside the damping device to the secondary flywheel disc and having radially on the outside extension arms which serve as biasing devices for the energy accumulator.
AS a further development according to the invention the input part of the primary flywheel disc can be a radially inwardly directed flange in the region of the axially aligned ring face holding the rotor wherein the flange is welded and/or staked to the platform.
The flange can form a positive locking connection by means of an external profile with the ring surface which has an internal profile.
On its inner circumference this radially inwardly directed flange contains extension arms corresponding in number to the energy accumulators which serve as biasing devices for the energy accumulators.
The output part of the secondary flywheel disc is formed in this embodiment by two side parts which contain chambers which are open on one side on the outer circumference and which contain the energy accumulators, wherein the number of chambers corresponds to the number of energy accumulators and the radially inwardly directed flange engages as the input part of the primary flywheel disc in the open side of the chambers.
One or both side parts forming the chambers can thereby be fixed on the secondary flywheel disc and/or on the contact pressure plate of the clutch wherein the secondary flywheel disc in this case consists of a bearing pin centring the clutch and of the clutch with the pressure plate which holds the side parts of the damping device.
To this end the fastening means of the side parts of the damping device advantageously engage through a number of oblong holes which corresponds to the number of fastening means whereby the oblong holes extend approximately evenly over a circumference over the angle of the relative maximum rotation between the primary and secondary flywheel discs so that a relative rotation of the two flywheel discs relative to each other remains and in order to maintain the play between the flange and side parts distance rings space out the side parts and the flange is supported axially against a plate spring and thus the play of the flange becomes fixed.
When using chambers filled with grease or oil it is advantageous to seal the chamber in order to prevent losses and leakage. For this the flange and side parts are sealed from each other by sealing means.
A seal of the chamber by sealing means between a side part and the flange on one side and between the flange and the radially inwardly extended bearing pin on the other side is also possible.
The sealing means are advantageously fixed by injection moulded parts which fit by means of axially imprinted noses in recesses provided in the flange, bearing pin and/or side part, and by means of at least one spring element on which they are supported against the flange, bearing pin and/or side part.
In order to configure the spatial arrangement according to the invention the shape of the secondary flywheel disc can be selected so that it extends frusto-conically in the axial direction with the tip of the truncated cone facing the primary flywheel disc.
In order to minimize the axial structural width and a neutral rotation behaviour the bearing of the flywheel discs on each other is preferably undertaken roughly at the same axial height as the central axial extension of the rotor and/or roughly at the same axial height as the central axial extension of the damping device. An arrangement of the rotor in a general manner on component parts belonging to the primary flywheel mass for optimising the axial structural space and cost-effective production can likewise be advantageous.
It is also advantageous to arrange the damping device at roughly the same axial height radially inside the rotor. The arrangement of the clutch is preferably radially inside the greatest axial extension of the stator belonging to the electric machine. Furthermore the damping device can be attached radially inside a clutch formed from at least two contact pressure plates with friction linings arranged inbetween, so that the axial structural space can be further reduced.
For a simplified fitting of the flywheel on the drive shaft recesses can be provided in the secondary flywheel disc for the assembly tools which can likewise be suitable for ventilating the radially inner region of the flywheel and the damping device.
The flywheel can be for example part of a drive train wherein the clutch directly follows the input shaft of the gearbox in the force flow or another unit connected in, such as for example a further clutch or additional flywheel.
To ensure the smoothest possible running the flywheel is balanced either with or without the fitted rotor, whereby the compensating weights are attached to the flywheel disc preferably on the support disc and/or on the side part forming the chamber for the damping device.